Using a semi-intact, behaving preparation of the CNS, cirri, and adductor scutorum muscle of the crustacean, Semibalanus cariosus, and pair-wise intracellular electrical recording, the objectives of the proposed research are: A). Continue identifying and characterizing motor neurons of three interrelated systems, the cirral contraction, the body and cirral hydrostatic extension, and the adductor scutorum muscle systems. B). Continue identifying and characterizing interneurons that are pre-synaptic to the motor neurons in an attempt to analyze the circuit/network that activates the patterned motor output that constitutes the normal fishing activity of the barnacle, and the circuit that generates the withdrawal-closure shadow reflex. C). Determine the detailed morphology of each of the neurons that are recorded from injecting cobalt salts via the recording electrode. D). Attempt to identify the neurotransmitters used in these central pathways by pair-wise intracellular recording while applying the appropriate pharmacological agents. E). Determine the functions of several central neurons with known morphology that are topographically identifiable from preparation to preparation. This study should contribute to understanding of the organization of motor systems by providing examples of the network(s) that control significant amounts of the animal's behavior.